Ductal branching morphogenesis is one of the many processes associated with the development of the prostate gland. An understanding of this developmental feature is important because it is responsible for the acquisition of adult glandular architecture and because inappropriate ductal branching appears to occur in prostatic disease. The embryonic urogenital sinus mesenchyme is essential for the development, growth and function of the prostatic epithelium. However, the structural organization and characteristics of the specific components of the prostatic stroma remain largely undefined. Since marked heterogeneity of ductal branching patterns occurs within different regions of the prostate, it is possible that variation in temporal and spatial organization of extracellular matrix proteins, and differential production of proteases associated with tissue remodeling, may be regulatory factors. To test this hypothesis, rat prostatic tissue will be examined for ultrastructural localization of specific components of the basal lamina and stroma, using quantitative,indirect, immunogold cytochemistry. This technique will be employed to study the organization of stromal components in the fetal and neonatal development of the gland, using dorsolateral and ventral tissue for comparison. In vitro organ culture will facilitate examination of branching morphogenesis at defined stages of pattern formation. To test whether regional differences in stromal tissue can modify branching patterns, heterotypic recombinants of dorsal epithelium and ventral urogenital mesenchyme will be either grafted into host animals or cultured,then examined by immunocytochemistry. It is anticipated that results from these studies will improve understanding of the normal morphogenesis of the prostate and lend insight into the possible mechanisms of abnormal growth patterns.